Telephone system



1,688,160 R. F. STEHLIK TELEPHONE SYSTEM Original Filed Aug. 22, 1924 4 Sheec,s-Sh.=.e'rl l Oct. 16, 1928'.

Oct. 16, 1928. 1,688,160

R. F. STEHLIK Y TELEPHONE SYSTEM Original Filed Aug. 22, 1924 4 Sheets-Sheet 2 Jmi uw, s, @i

'Oct 16, 1928.

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Patented Oct. 16, 1928..

UNITED STATES WARE.

PATENT ferri-CE.

nUnonrH F. sTEHLIK", or CHICAGO, "ILLINOIS, AssIGNonjBY MEsNE ASSIGNMENTS, i

To AUTOMATIC ELEcTRIo INC., oroHIcAGo, ILLINoIs, A CORPQRATIQNy 0F DELA'.

TELEPHONE SYSTEM.

applicativa flied August 22, 1924, serial Ita-733,471. Renewed May v, v192s.

The present invention relates in general vto telephone systems, but is concerned more par ticularlywith telephone systems oi the type in which so-called finder switches, i@ e., backward hunting switches, areemployedto connect a calling line with an idle trunk; and the principal object, briefly stated, is the pro duction of a new and improved linder system employing primary finders which are di rected in their movements by registering equipment operated from the calling` line, and employing also secondary finders which are not directed but perfo-rm the usual testing operation to determine the extent of their hunting movement. f

One of the main features of this invention is that the common line relays', of which there are twenty for each group of one hundred lines, are used as counting relays to count off the impulses transmitted to a primary linder as it is being directedtothe callingline. A

Another feature of this invention lrelates to the provision of novel circuit arrange ments whereby the negative line conductors are normally connected tothe common tens line relays and are switched to the units line relays as soon as the tens registration is completed. -v Y A further feature of the invention relates to the provision, in connection with the twin f finder allotters which operate in conjunction with eachother toallot one idle finder of aY group as large as the'combined capacity -o-f both allotters, of means whereby these `finder allotters are electrically interlocked so as to cause them to operate in synchronism with each other to prevent simultaneous allvottation by both allotters. Y Y

A further feature relates to the centralized control of the switch-through operation which is performed only a ter a primary finder has found the calling line and asecondary finder has found the primary finder;

There are various other features of the in vention, having to do,` however, for the ino-st part, wit-h the circuit details `involved in carrying' out the features hereinbefore set forth, which, together with the foregoing, 'will be explained fully hereinafter. Y

Referringnow to the accompanying drawings, comprising,- Figs. 1-4, inclusive, which show by means of the usual circuit diagrams a sufficient amount of apparatus in a sys tem embodyingthe principlesof the .invention to `enable thejmvention to loel understood and its utility appreciated, Fig. l shows the primary `finder PF which has access to the line of substation A; Fig. Qshows the second-ary "linder allo-tter SFA and -the secondary finder SF which has access to the primary `finder PF, and which is linked to the selector S; Fig. 3 shows the common line relays (which are subsequently used as impulse counting relays), `together with cer-y tain auxiliary relays; and Fig. 4 shows the primary finder allotters` PFA-l and PFA-Q, together with the associated allotter control and sending control relays.

Regarding the equipment shown-r `in the drawings, it may be pointed out that the substation A is of the usual automatic type;

that the primary finder PF, together withv the selector S, is of the well known vertical and rotary type of automatic `switch and has 4its bank contacts r arranged in i' horizontal rows or levels; `and that the secondaryfinder SF,

SFA and the primary l.finder allotters PFA-1 and PFA-f2, are ofthe well known Y:rotary type of switch in which the Wipers movein aforward directiononly and advance siXth level of theiprimary finder PF. as is denoted by the number 601placed to theleft of substation A, desires to make a call.y o Accordingly, the subscriber at substation A removes his receiver, thereby placing'a direct current bridge across'conductors `2 and 3. The positive conductor Slof the` line of substationlA is connected'through the resting Contactr and armature (lof the cut-off relay il,

and conductor 8 to the sixt-h.positivecommon line conductor '206,y kwhich is grounded through resting contactland an armature "of relay 251. Accordingly, a circuitis closed through` theV 'calling line andy over thenegative lineconductor 2, restmggcontact and armature 5, conductor'l', armature 254 and Y its resting contact, andconductor 216 for both windings of the sixth tens relay 236. Relay Qthereupon energizes` and locks .itself at 'together'with the secondaryfinder allotter `nates in the tenth set ofbank contacts inthe armature 255 and through the locking chain circuitto the'yholding conductor 288 which is grounded through'the resting contact and armature 316 of relay 303, Fig. 4, and armaturev328and itsresting contact. Armature 25,5'of'1theftens relay 236 also 'opens at this 'po'int'the locking `chain circuit'which isv proture 258. Thefactth'at the tens operating )conductor 281 is grounded by the sixth Itens relay 236l and' not by some other tens relay pre-determines that the tens-digit to be trans- ,Y -mittedvis the tens digit 6 as will hereinafter Asia still vfurther result of theenergization .ofl relay 236,'it closes at armature 255 a 'circuit for relay .251 which thereupon enerfgizesland removes ground from conductors 201-210, inclusive,A leaving conductor 206,'v however` grounded atarmatureU259-of relay 25 236. As a further result-of the energization of relay'251, it closes at its innerv upper armature a circuit fromthe grounded holding con- Uductor 288 for themulti-contact transfer re- 30. lay v2531which thereupon energizes and locks itself `toground through-the lower armature and working contact of relayr251, at the same time opening its initial circuit. u Relay 253 transfersthe one hundred negative conduc- 'tors,rofiwhich conductor 7y is one, from the tens yoperatii'ig vconductors 211-220, inclusive, to the units operating conductors 221-230,

A inclusive;y 'Responsive to this operation,the tenth unitslrelay 250 'energizes over the fol- -lowng circuit: from kground by Way of arman ture 259 of the sixth tens relay 236y audits workingcontact, conductor 206, conductor 8,

armature' and its resting contact, the callving line, resting contactand armature 5, conductor 7 armature 254 audits working contact, the tenth units conductor 230, the associated armature andzresting,contacts of relay fi 252, and relay 4250 to battery. Upon energiz- 5'0 ductor 284 `is grounded by the units relay 250l and not byQsome other units relay prefdetere i mines thattlie units digit to be transmitted..`

ing, relay 250 places ground upon the unitsl operating'conductor `284 at its upper armature. The fact that the units operating consubsequently is tlie'units digit 0 as will'hereina'fter appear.

"to the'grounded conductor 288 at its lower ingacircuit yfor the cut-off relay252. Relay armature, and at its middle armatureplaces ground` on start conductor 285, thereby Vclos- 252 thereupon energizes and disconnects the units" conductors 221-230,inclusive, fromv r` the"corre'sponding units relays 2414250, ,in` time, owingzto-tlie fact that the initial circlusive Relay 252 also closes a-inultiple circuitfor relay 253atj its ,uppervarmature for reasons that will appear hereinafter.

Relay 'i250 also locks itself.

As a further result of the placing of the `lVi1jei-3`58 of the primary, finder allotter .PFA-Zat this time is outof engagement with its bank and accordingly nothing happens ;responsive to ground being placed thereon. Howeveig wiperv348k of theA primary ynder:allotter RFA- 1 is in engagement with the first Contactin its bank and the ground potential 1s extended over conductor 4G to relay r23.0frthe allotted primary linde'r PF. y

Accordingly, relay'23 energizes and prepares the inderpfoi operation and connects up'the common.conductors 41 and42, and 44 and 45. Asa still further result of the energization of startrelay 304, 4, it closes at armature 319 yand its right hand working Contact a yciicuitlfor the upper Winding of the twostep relay 301 as follows :from ground by way of contactpand.theupper windingof relay r301 i' Vto battery. Relay 301 now energizes, but,

owing to the fact that the upper Winding of relay 301 comprises a comparatively small numberfofturns of wire having a relatively high resistance', relay 3,01 energizes rather weakly and operates only its first step armature 312 which closes a locking circuit forthe ylower Winding through the working contact andy armature 322. However, as long as the lill initial circuitof the upper winding of relay 301 is established, thelower Winding ofthe said relay 301 is short cirCuited.

Asa still further result of the energization of the starty relay 304, it places ground on the interrupter 339 at armature 319 and its left f hand working Vcontact in order to start the sending operation. Accordingly, as soon as the interruptor 339 is closed acircuit is closed through armature 310 and its resting contact,

tens operating conductor282, the corresponding armature andits resting Contact of ielay 261, and the upper winding K'of the tens "pick-up relay 261V to battery. Relay 261 also is a tivo step relay and, therefore, enerv `gizes only enough to operate its lower armacuitiisstill established, andthe. ground'poten- Y Vnet 26 ot the primarj-,f inder PF, Fig. 1.

ings short circuits the lower winding ot the re! r 283 to the common vertical magnet operatingl conductor l2, Fig. fl, which is at this time connected with vertical magi'iet 26 ot the primary iinder PF, Fig. 1, through the working contact and armature 38 of relay 23. Accordingly, upon the next closure of the 'interrupter 389, the ground potential which is placed on conductor 282 is extended by'way ot conductor 283 to the vertical magnet operan ing` conductor /1-2 and thence to vertical m ag The momentary application ot Iground to condire tor 282A is effective also in operating relayl 262 through its tirst step to close a locking circuit for itseliL1 at its lower armature, and when the ground potential is removed from conductor 282 relayA 262 energizes completely and removes ground at its upper armature from the contact ot the secondiarmature, counting from the top,`oit` relay 231. This latter operation, however, does not have any particular utility at this time on account ot the tact that relay 231 is not the tens relay which is' energized. In addition, relay 262 closes at its upper armature a circuit tor relay 263 which energizes and connects conductor 288 with the lower armatures ol' relays 2532-2110. inclusive, over a path that is exclusive of the lower armatures ot relays 231-239, inclusive.V Relay 262 also extends conductor 283 to the lirst tens relay 231.

Similarly, upon the next momentary application ot ground potential to conductor 282 by the interruptor 339, an impulse ol? current is again transmitted to the vertical magnet 26 yo-lE the primary finder PF, Fig. 1, `and a circuit is closedthrough the upper winding otr-clay 231 to operate the relay through its lirst step, and at the terminationot the momentaryr application otground potential rerelav 232 for operation.

This operation continues asy described until sin impulses of `current haveheen delivered to vertical magnet 26, at which time the tens relays `232-23l, inclusive, in addition tothe tens relay 231, have been operated fully and the tens relay 235 is energized through its `first step. At the end` ol the sixth impulse transmitted to vertical magnet 26, ground is again removed from conductor 282 by the inlay 231-energizes completely and prepares terrupter 339, whereupon. the fifth tens relay 235 energizes completely and'at its third armature, counting ronr the top, removes ground from the tens operating conductor 281, ground having been supplied previously, as hereinbetore pointed out, through the armature in question and yits resting contact, and the working contact and armature 258 of the sixth tens relay 236.

Responsive to the six impulses ofcurrent delivered to it, vertical magnet 26 of the finder PF raises the wipers 71-73, inclusive, step by step and they come to rest opposite the sixth levelof bank contacts.

Responsive tothe removal of ground potential from the tens operating conductor 281, the interrupter 339 is rendered ineffective to further operate the vertical magnet of the primary finder PF, and the lower winding ot' relay 301, Fig. Il, loeing no longer short,V circuited, energizes 1n series with the upper winding of the relayand operates the armature proper through its second step. At armature 311 relay 301 disconnects the right hand working contact of relay 319 from the junction of its own windings andiconnects it instead to the junction of the windings of relay 302; disconnects the interruptor 339 from the tens operating conductor 282 at armature 310 and connects it instead to the units operating conductor 286; and at Varmature 309 disconnects armature 319 of relay 304: from the tens ground conductor 281 and connectsit in stead to the units ground conductor 284. Then this occurs armature 319 is grounded again through conductor 2811,' and the interruptor 339 again becomes effective. Also, a

circuit is closed through the right hand working contact of relay 319 and armature 311 and its working Contact for the two-step relay 302, which thereupon energizes through its first step as pointed out in connection with relay yUpon the first closure of the interrupter 339 subsequent to the above mentioned operation o relay 301 through its secondstep, a circuit isV closed through armature 310"k and its working contact and over the units operating conductor 286 for the upper winding of the two-step units pick-up relay 264, which thereupon energizes part way only, as pointed out in connection with the corresponding tens pick-up relay 261. Accordingly, at the end ot this closure o'li the interrupter r339, relay 2611 energizes Jfully and disconnects the units operating conductor 286 from the junction of y its own windings and connects'it instead to the corresponding armature of relay 265 and to conductor `87 which is connected to the rotary'niagnet operating conductor 41, Fig. 4l.

Upon the next closure of the interriipter 339. Ground is again placed' upon the units operating conductor 286 momentarily andthe upper winding of relay 265 is energized, op eratingthe relay through its first step. Also,

lin

ground is placed through conductor y287 on the Vcommon rotary magnet `operating conductor 41,` thereby closing a circuit through the Working contact and armature 39 ot' relay 23 oi'f 'the primary finder PF, Fig. 1tor the rotary magnet 271; At the end of this momentary application of' ground to conductor 286, relay 265 energifzescompletely and extends conductor 230 Vto the upper winding of the iirst'units lo,

'closes a circuit for relay 266 which energizes relay 241. At its upper armature, relay 265 and shunts the associated chain circuit.

' rIn'the v,above manner the relays 242-249, inclusive, are operated, and as relav 2491s operated'through its iirststep the tenth impulse of current is delivered to rotary'magnet`27 over the'falt-ove pointed out path. At' the opening oit' the interrnpter 339 'following the 'f the working contact andupper armature-,of

. tenth impulse to rotary magnet 27 of theY pri-V mary 'Finder FF,Fig.-1, the two-step relay 249 ei'iergizes Athrough its second step and at its middle upper armature removes ground from theI tenth' units relay '250 and, accordingly,

' from theunits groundlconductor 234,

- In the primary nder PF, th'e'rotary magnet 27 energizes responsive to each of the ten impulses 'of current delivered to it-and rotates the wipers 71-73, inclusive, step by step until they come into engagement with .the tenth set of ba'nk'contacts in thosixth levehwhich is fthe contacts 9-11, 'finclusive, associated tive and the two-step vrelay 302 operates fullypreparatoryto operating the switching relay 'start conductor 52 of the iinder.

with the line of. substation A.

As a result ot the ground potential being removed from the umtsv ground conductor 284, the interrupter 330 is rendered ineffecthrough its two windings in series, owing to thefact that its lower winding is noV longer,

short circuited. At its upper: armature v313 relay 3D2-:places ground upon conductor 332 21 of the primary finder PF, Fig. 1. However, assuming that a secondary Vfinder has not yet foundithe trunk'associated with the primary finder PF, they secondary testielay 305 is not yet energized and the switch-r ture v320 places ground through armature 325 andy its resting Contact on the common con-v g ductor- 44,thereby extending'groui'id through armature 41 oit relay 23 of the primary lin der PF, Fig. 1,*to the individual secondary finder W'henithis occurs, a circuit is closed through the jumper a 08,'the c'onnnon secondary group startv condu'ctor', and the resting contact and arma- Also, it may be'pointedv out that mosaico ture G ior-startrelay148015 the secondary rfinder allotter SFA. Start relay 148 thererupon energizes; rapplies ground atarmature 154 to test wiper 142 through test relay 147 yand at armature 153 connects the interrupter 150to stepping magnet 104` of the secondary finderl SF through wiper 141 and 'the'bank contact on which it is standing. Accordingly, stepping magnet104advances the Wipers 101-103, inclusive, step by step ina search ofl the primary hnderk PF under :the control of the interrupter 150.

vThen the-wipers 1014103, inclusive, ar-

"rive upon the bank contacts in which con-k ductors -57, inclusive, terminate, a circuit is completed for test yrelay 147 as follows: from ground'byway of the working contact and armature 154 ofstart'relay 14S, test relay 147, normally closed contacts controlled by armature 151,'wiper 142, the bank contacts.`

uponwhicliit isastanding, test Wiper 102 of the secondaryfmder SF, the bankcontact uponv rwhich fit is standing, conductor 5G, Jumper 06, conductor 50, ar1nature36 of relay 23 and`M its working contact, the common test' conductor 45, and relay 305 and resistance `331, Fig. 4,1 in multiple to battery. Responsive to the closure of this circuit test relay 147 energizes and at armature ll-disconnects the interrupter 150 from magnet 104 fof the secondary nder SF, and closes a locking circuitlfor itself through magnet104, at the 'same time 'disconnectingits own Winding from wiper 142.A vRelayi147 also applies ground to wiper 143, therebyclosing a circuit for the secondary finder connecting relay 105.

Relay rthereupon energizes; connects up its line wipers 101 and 103 at armatures 109 and 108; connects the'release trunk conductor y113 oftheassociated selector `S withy the test wiperf`102 at armature 10G yand atr armature 107, connects ground to release trunk conductor 113 and to test wiper 102.A Y

Regarding the secondary testsrelay 305, Fig. 4, it may be pointed out that this. relay l is shunted by the non-inductive resistance 331 in order to permit the test relay 147y of the secondary finder allotter SFA, Fig.2, to energize rquickly over the above traced circuit.

Accordinglyq relay 305 will probably not opr` erate as quickly as relay 147 and will remain unoperated whilerelay 147 is energizing and becoming lockedup, asl hereinbefore pointed out. fHowever, when the directground poJ tential isplaced upon test 'wiper 102of the secondary tinder SF by relay 105, as Vpointed outabove. test relay 305,Fig` 4, energizes quickly. Upon energizing,`relay 305 disconnects Iground from thecommon start conductor 44 and closesa locking circuit for itself.v

at armature 325. Accordingly, ground Vis extended through conductor 45,' Working contact and armature 36,conductor 50, jumper 60 and conductorto test-,wiper 102 of the secondaryfindery SF, thereby providing ai nient `with the `next setof bank contacts.

holdingcircuit for relay 105 Vthrough armature 106 and its working contact and the Working contact and armature 107 independ,l

ent of the ground supplied to relay 105 i'roin relay 147 through Wiper 143.

As a result of the ground potential being placed upon release trunk conductor 113 of the selector S by the operation of relay 105, as above pointed out, a circuitis closed through Wiper 144 of the secondary lind'er allotter SFA Jr'or the start-relay-disconnect rela-y 149 and for stepping niagnet'l45 in multiple. Relay 149, upon energizing, disconnects start relay 148 at armature 156. Start relay 148, hoivever,being slow acting, does not fall back immediately.y Stepping magnet 145, upon energizing, attracts its armature preparatory to advancing the Wip ers 141-144, inclusive, but does not advance these Wipers upon its forward stroke. Stepping magnet 145 opens a point in its oWn circuitat armature 146, but does not open itsoivn circuit on account of the fact that the interiupter contacts 146 are at this time sliunted by armature 155 and its Working contact. Y.

Vlien start relay 143 finally falls back, it opens the circuit of test relay 147 at armature 154, whereupon relay 147 deenergizes and removes ground from Wiper 143 at armature 152, leavingc relay 105 locked up from the ground potential coming over the her inbefore traced circuit from the secondary test relay 305, Fig. 4. Test relay 147 also removes the shunt troni around the interruptor contacts 146 at armature 155, whereupon step ping magnet 145 deenergizes and advances the wipers 141444, inclusive,`into engage- It the finder` associated with this next set of bank contacts is idle the stepping inagnet145k is not again operated and relay 149 deenergizes and connects start relay 14S to the start conductor 58 again. llfoivever, it the linderis busy, test wiper 144 engages a ground po-v tential upon the test contact thereof; `relay 149 remains energized kand steppinginagnet 145 operates again to advance the ivipers to the next contact. This operation continues until an idle inder is tonnel, Vwhereupon Atest Wiper 144 engages` an ungroundedV contact,

steppinginagiiet 145 ceases to operate; and relay 149 deenergizes and connects start ren lay 14S to start conductor 58 again. y

Referring` noivagain to Fig. 4, as a further result of the energization of relay 305, it connects the grounded l conductor 332 tothe allotteil test relay 346 at armature 324,ivhereupon relay 346 eiierg'izes and closes at armature352 a circuit for stepping magnets 349 and 354 in inult-iple. These stepping magnets4 thereupon energize preparatory to advancing' their respective Wipers. l.Asa `still further result of the ei'iergizatioii et krelay 305,!'1t

connectsat armature 323 ground frointhe" 264, 265 and 266 de'energize.

347 is in engagement .with the bank contact in which the switchingjeonductor 47 Ot the` primary finder PF terminates.- Accordingly, the `ground potential is extendedf'to rthe switching conductor 47, and switching relay 21 ot the primary finder PF energizes through off normal contacts 30 and armature 37and`its Working contact,` Upon energizing, relay v21 locks itself to the release trunk conductor 50 of the primary nder PF, Which is, at this time grounded over conductor 45 by the secondary ytest relay 305, Fig. 4, as hereinbeliore pointed out. Relay 21 also places ground upon test Wiper 72 of the finder at armature 33, whereupon the cut-oill relay 4 of the calling line energizes and disconnects the conductors 7 and Sironi the callingjline at armatures 5 ando, respectively, Relay 21 also connects up the line Wipers l71 and 73 at armatures 34 and 40, respectively. llien this occurs, the line relay 121 of the selector S energizes over `the calling line through bank contact-s 9 and 11, Wipers 71 and 7 3, armatures 34 and 40 and their Working contacts, conductors 49l and 51, jumpers 65 and 67, conductors 55 and 57, the bank contacts in which these conductors terminate, Wipers 101 and 103, armatures 109 and 108 and their Working contacts, conductors 112 and 114, and armatures 126 and 129and their restingcontacts. Line relay 121,:up`on energizing, closes at armature 124 'a circuit for release relay. 122 Which thereupon energizes and places ground upon release trunk conductor 113 at armature 125, so :is to maintain the calling line in connection with the first selector after theground potential placed on the release trunk conductor through the medium ofthe primary i'inder allotter PFA--l has disappeared.

Referring now again lto Fig. 4, as a further result of the operation of armature 32401 the secondary test relay 305,the Windingof relay 303 is energized in multiple rwith the alletter test relay 346 through the Working contact and armature 318 ot relay 304. IUpon energizing, relay 303 disconnects start concluetor 285 at armature 315 from start relay 304. Start relay 304, being slow acting, does not' deenergize immediately `following its disconfi nection at armature 315. As a further `result of the energization ofifelay-303,y ground is removed from theholding conductor 288 `at armature 316, whereupon the ytens relays 231-236, inclusive, relays 261', 2.62 and 263, the unitsrelays241-250, inclusive, and relays VUpon' the deenergization of theteiis relays, the circuit of relay` 251 is opened.k Relay 251 deenergizes and again grounds the conduc-y tors 2014210, inclusive, at. the V same .tiinef opening the initial circuit orelay 253, leavarmature 318. Relay' 304 Valso deenergizing, remove ground from start conductor 285, leaving'r this conductor grounded, however, at armature 315 of relay 303, F1g.,4. Accordingly, relays /252and 253 remain ener-` gized and lno' other number can as yet be regis' tered. f l

vVVh'en start relay 304, 4, iinally falls back, it disconnects the winding or'- relay 303 from inmultiple with test relay 346 and connects it to the grounded test wiper 347 at removes ground from conductor 290 at armature 322, whereupon relays 301 and 302 dee'nergiz'e.` Startrelay 304 also removes ground from wiper 348 of the vallotter PFA-1, whereupon the holdingrelay 23 of the primary finder PFfd'c'energizes and places ground at armature 37upon test conductor 47 through the olil normal contacts 30 so as to maintain the primary nder PF busy to the primary allotter PFA- 1 until the primary finder PF has become ridle andlhas beenA restored to its normal position. A As a'. further result or' the deenergization of start relay 304 it opens the locking circuit of relay 305 at armature 320,- whereupon relay 305 deenergiz'es.

As a result of the deenergi'zation of relay 302 and ofthe deene'rgization of relay 305, the local circuit ofthe allotter test relay 346 is opened at karmatures 313 and 324. When this occurs, the test relay 346 Adeenergizes, regardless or the 'fact that test *wiper 347 is in engagement with a 'grounded bank contact, because the interrupter contacts 350 and 355 are` open. Upon' deenergizing, relay 346 op'ensthecircuit or' magnets 349 and 354, whereupon these magnets tl'eenergize, and each 'advances its respective wipers onestep.

y In tliisfcase the wipers 357 and 358 of the primaryl linder allotter- 'PFA-2 arey advanced still urtheroif their bank contacts, and the wipers 347 and 348 of the primary finder PFA- 1 are advanced into engagement'. with the second set of bank contacts. Assuming that the primary finder associated with thisse'cond set'or' bank contacts is idle, the test conductor thereof corresponding to test conductor 47'` isr ungrounded and test relayy 346 is not again energized, permitting the allotters rto remain where theyare.

` Also,relay 303, which is new connected to test wiper347, deenergizes and disconnects start conductor 285 from ground andcoimects it to start relay 304 again. Y Y Relays 252 and 253, Fig..2, now deenergize to permit vthe number of the next 4calling line to be registered. K 1 Referring now to the' connection which is being established, the subscriber at substation A" may now vmanipulate his calling vdevi'cefin accordance with.l thefirst digitin the desired number. When he does so, one or moreinterruptions are produced in the circuit or line relay 121 of the selector S, Fig. 2. Accordingly, line relay'121'deenergizes one or more times and causes the wipers 130-132, inclusive, to be raised opposite the desired level of bank contacts in the usual and well known manner. The selector 'S now rotates i'tswipers 130s-132, inclusive, automatically in search'of an idle trunk. Then an idle trunk is reached, which trunk it will be assumed is the onecomprising conductors 133-135, inclusive, the switching relay 123 energizes in the usual manner; opens the circ'ui-t of theslow acting release relay 122 at armature 128; opens the test circuit and prepares the holding circuit atfarinature 127; and at armatures 126 and 129, disconnects conductors'112 and 114 from thewindings of line relay 121 and extends them by way of wipers 130 and 132, the bank contacts upon which they are standing, and Aconductors 133 and 135 to the windings of the line relay associated with. the seized trunk.-

The line and release relays (not shown) of the seized trunk now energize and the latter places ground upon release trunk'co'nductor 134, thereby establishing' the usual holding circuit; i n The calling subscriber may now manipulate his calling device in accordance-with the re-y maining digits in the desired number and thereby complete the connection.

lVhen the subscriber at substation A re-' places his receiverrai'ter the conversation is terminated, ground isV removed from release trunk conductor 134 of the trunk seized by the selector S,Fig. 2, in the well known manner, whereupon switching relay123 of the selector S, relay 105 of the secondary finder SF, switching relay 21 or the primary iinder PF, and cut-off relay 4 or' the calling line deenergize. Responsive to the deenergization or switching relay 123 of the selector S, the said selector is restored to normal posiA tion in the usual manner.

Responsive to the de'energization ol switchingrelay 21 ofthev primary iinder PF, the release magnet 24 is energized over the followingk circuit:v from ground by way or larn'i'ature 111 of the secondary group busying relay 1107 Fig. 2, and its resting contact, con-k ductor 54, jumper r64, conductor 48', spring 29 ot the push button 28 and its lower contact, armature 35 and its resting contact,l yresting lll) contact and armature 31,01i normal springl 25v and ritsup'per conta-ct, and release magnet 24 to battery. Upon energizing over this circuit, release magnet 24 restores the wipers 71- 73, inclusive to normalposition in the usual manner." The circuit of release magnet 24 is opened by ofi normal spring 25 when the wipers reach vtheir normal position.

The manner in which a. typical connection is established having been described, cert-ain fr line as hereinbeiore pointed out.

points not fully brought out in the foregoing will nowbe taken up. f

In connnercial systems ofthis general type, itis generallyk considered to be essential that provisions bemade to prevent the wrong op-y eration ot' a linder when two lines accessible thereto and located in different tens groups arey calling simultaneously. Otherwise' the numbers of the two lines might become broken up or scrambled, so to speak. The way in which this is prevented in the present system will new be explained. For this purpose it will be assumed that the subscriber at sub station A, whese line is No.6() from the standpoint ot' the primary finder PF, removes his receiver and that the subscriber on line No.y 7l removes his receiver siiinilt-aiieously. Aceordingly, the sixth tens relay 236, Fig. 3, energizes over the line of substation Ain the hereinbefore described manner, and the seventh tens relay 237 Venergizes simultane#` ously. Relay 236, upon energizing, closes a locking circuit for itself at armature 255, at the same time removing ground fromv the corresponding locking armature of relay 237. Therefore, relay 236 alone locks itseltener# gized.` Relays 236 and 237 close a circuit ter relay 251, whereupon relay 251 energizes and removes ground from conductors 29l-'2l0, in-y clusive, leaving the sixth `conductor 205 grounded'however, through armature 259 and its working contact of the sixth tens relay 286.` rllhere is no ground on the seventh' conductor 207, however, regardless ot the tact that relay 297 is energized, owing to the tact that ground is disconnected from the upper armature oit relay 237 at armature 259 of relay 236. Relay 251 also closes at its lewer armature av circuitA for the multi-contact transfer relay 253, whereupon conductora? and the similar' conductors of the other lines are disconnected 4from the tens relays and transferred to the units relays; The tenth units relay 250 new energize's over the calling The `first units relay 2LH, however, does not energize, even though the subscriber on line 7l has his receiver olil the hook, because of' the fac that the positive conductor et the calling line' 7l is vnow ungroundecl. because ground is removed from the corresponding cenducter it being understood that the positive `conducters of all lines whose first digit is i' are connected to conductory 207 through the contacts ot their respective cut-ott" relays in the same manner thatV the positive conductor ot' the line of substation Aisfconneeted to conductorv 296 through the contacts on the cut-` ofl relay 4l'. It willl be understood also that relay' 237, not being locked up, fallsk back upon the above described energization of relay A further point somewhat related to the one explained above is that in case two lines in the same'tens' group are calling simultaneeusly only the lowest number is registered, owing to the fact that each units relay, barring the last, removes ground from the lock#` ing armature ofthe next units relay. Ac-y cordingly, as soonlas the eut-.off relay 252 en-y ergizes the'relay which is not locked up falls back leaving the other units relay locked up.

It sometimes happens thatY a subscriber takes olif` his receiver rand replaces it again without actually making a call. He may do this so quiclrlythat tens relay becomes loclred up, but su'lilcient time is not allowed for a units relay toloperate.` t is, accord-l ingly, desirable to automatically unlock the tens relay at'terfa slight interval so thatthe next calling line mayenergize the Correct tens relay. Accordingly upon any tens .relay energizing, timing conductor 289 is grounded throngh'the upper armature and resting contact of relay 261, closing a circuit for the slow to pull up relay 308. Relay. 308 energizes after a slight interval and closes a eircuit iorrelay 307 atarmature 329. Relay BOT, accordingly, energises after a momentary interval and removes ground from the holding conductor'288 at armature 828m case start relay 304' has not become energized. Responsive to the removaly of ground from' conducto-r 288, thel'loclred'up tens relay deenergizes and `removes'ground'from the timing conductor 289, -whereupon relays S and 307 fall back one after the other and relay 397 replaces ground upon conductor 288.'

lt may happen occasienallyftnat a primary iinder, such for example as the primary iinder FF Fig. l, tinds the calling line but the primary iineer'is not in turnound by a sec-A o-ndary finder, .such for example asthe secondaryA iinder Sli`,rFig.2. ln this case, itl special provisions were'notfmade the entirer group Vwould be tied up andrendered inoperative because the registering relays are loclcdfup and are notunlockedordinarily until the primary iinder has found the calling line and lhas been'r found by a vsecondary under. Then such a contingency arises, however, a s pecialtiiningarrangement in! cluding relays 30G-308, inclusive, comes into play after suli'icient time-ha'sbeen allowed for a secondary iinder to find theprimary iinder anldfcauses Vthe allotters to 'be vladvanced and the register relays tobe unlocked.Y Thefway in which this is accomplishedwill now be exi plained. It has. been pointedfout vhereinbetore that conductor 288: isgrounded upon the energiz'ation o t any one ot the commony tens relays ot Fig. `3, and'that relays'SOT and 308 energize as a result'. VAs a further result yof the energizati'on of relay 307, it closes a cir- Vcuit for the slow acting relay 306 at armature 327, whereupon relay 306 energizesland disconnects conductor from the working contact of armature 818 at armature 326, so as to prevent a premature advance eiftlie al- .letters New, k when pick-up" relayv 261, Fig.

lll)

v'3, energizes, it opens the circuit of relay 308:

` justed, the three relays 306-308, inclusive,

are deenergized. The adjustment of these relays is such that this total time is suiicient to` permita secondary' finder to ind a primary linder, allowing the maximum required limiting time. Upon deenergizing, relay 306 closes at armature 326 a circuit for test relay 346 whichhas been prepared at armature 313, whereupon test relay 346 energizes and closes at armature 352 a circuit for stepping magnets 349 and 354 in multiple. These magnets accordingly energize preparatory to the advance of the associated wipers. The winding of relay 303 is energized in multiple with relay 346 through the working contact and armature 318 and removes ground from the locking conductor 288 at armature 316 and at armature 3151 disconnects start relay 304'wit-h the result that start relay'304 deenergizes after aslight interval and opens the circuit of relay 302 at armature 322 which deenergzes and opens the circuit of relays 303 Vand 346 at armature 313, whereupon relay 346 deenergizes and opens the circ-uit oic stepping magnets 349 and 354 at armature 352 whereupon the said stepping magnets deenergize and the allotters are advanced in the usual manner one step.

Responsive4 to the removal of the ground potential from conductor 288, the locked up tens and units relays deenergize and, respon` sive to the removal of ground from conductorr285 at armature315, relays 252 and 253, Fig. 3, deenergize, permitting the number of the calling line to be registered again with the result that the sending operation is started all over4 again and the newly allotted primary finder finds the calling line and a secondary linder in the associated group linds the primary finder in the manner hereinbefore described. e

The manner in which the two `primary finder allotters PFA-l and PFA-2 are kept in exact step with each other will now vbe pointed out. For this purpose it will be assumed that the two allot-ters are advanced one stepl automatically from their position shown in the drawing in the h'ereinbeiore,described manner and thatfthe finders associated with the next three or four contacts inthe bank of thea-llotter PFA-1 are busy. Accord ingly, test wiper 347 engages a grounded test contact and the winding of relay 303 is n maintained energized rthrough the resting contact and armature 318 and maintainsthe start conductor 285 grounded and start relay 304 disconnected at armature 315, and conductor- '288 ungrounded at armature 316. Under this condition,when both steppingV magnets 349 and 354 have restored to their normal position, a circuit is closed fortest relay 346 in multiple with the upper wind-V f ing oli-relay 303` through contacts 350 and 355. When this occurs,.and not until this occurs, stepping relay 346 energizes again and again closes the circuit of the stepping magnets at armatureL 352at the same time closinga lockfy ingcircuit for itself at armature This locking circuitremains established until both magnets have energized liar enough to permit, theirrespective pawls to reach engage the next notch on its associated ratchet wheel. fWhen this occurs, the circuit ot'estepping relay 346 is opened at contacts 351 and 356 and the said relay 346 deenergizes and opensthe kcircuit or' the stepping magnets 349 and 354, where-y upon the said magnets deenergize and each advances the respective associated wipers another step. This operation continues as described until wiper 347 engages an un,- grounded bank contact at which point relay 346 fails to energize again and relay 303 dek energizes to permit the next call to be handled by the newly allotted linder. i

. From the foregoing it will be seen that the circuit of the magnets 349A and 354 and the c controlling relay 346 are so inter-locked that relay 346cannot energize to energize the step'- ping magnets for the next stroke until both n magnets have restored their armatures and advanced the wipers to the desired set of contacts, and that, having once energized, relay 346 remains locked up until both magnets have operated suliiciently to insure that the wipers of .both allotters will be advanced when the magnets fall back.

Referring now. particularly to Figs. 1 and 2, the trunking arrangement between the primary and secondary inders will be explained more in detail. It will be understood, of course, that the secondary linder SF is merely one finder of the group of finders having access to the primary finder PF, Fig. 1, and others. There are a plurality of such groups of secondary finders, because one group of finders can have access to only a limited number of primary finders. It it is assumed that there are lifteen groups of secondary linders and thatthere are thirty primary finders, such as the-primary finder' PF, Fig. 1, all having access to the same group of subscribers lines, then two primary finders in this group are allotted to each secondary group. This. of course, is the usual expedient made use of in order to increase the trunking efliciency by varranging' it so that a, call from any line any one of the `fifteen groups.

In order to enable vthe primaryiinders to be cross-connected at will to the `secondary lindersrin accordance with any, desired ar'- rangement when the system is first installed and later to take care ot growth and traffic changes, the'intermediate distributing frame IDF .has been provided and yeach primary finder is connected to the left yhand side of the `frame in the manner shown in the draw- .mayv be completed by Va seconda-ry finder in Vas the common start conductor 1,688,1eof y ings. Similarly, the banl; contacts of the secondary finder are connected to the right hand side of the intermediate distributing frame in the manner shown.V The same appliesto the common start conductors of the Various secondary groups, such, for example, of the secondary group in which the secondary finder SF is located. rllhe same applies to the conductors 53 and 54 associated with the malte-busy relay llO.

lt will'be noted that there are sin conductors coming from the primary finder Pl? to the intermediate distributing frame, which are connected by means of the jumpers (i3-68, inclusive.` to six conductors on the opl posite side of the frame. Accordingly, it is preferable that the terminals on the intermediate distributing frame are arranged in ,'jroupsv of sinv terminals each. This, however, is for convenience only and any other desired arrangement maybe employed. Assuming, however, that the terminals are so arranged, three terminals in each group on the right hand side of the intermediate distributing frame represent the line and release trunk conductors coming from the baul; contacts of a group ofsecondary finders; another represents the common start con` doctor of the associated group; while the remaining two represent contacts on the make-busy relay of the associated secondary Group. FromV this. it` will be seen that the vcommon start conductor 58 is connected to that the conductors associated with ltheprimary finders are connected toene side of the intermediate distributing frame to termi.- nals segregated in groups of six, one group for each finder, and that the bank conductors and associated conductors of the secondary .finders are similarlyconnected to the opposite side of the frame. Accordingly, any primary linder can be readily cross-connected to any group of secondary finders by means of jumpers, such as the jumpers (S3-68,' inelusive. s

`With the foregoing explanation in min l, the operations accompanying an all-trunksbusy condition in a group of secondary find` ors, may be readily understood. Assuming now that each secondary finder and associated selector in the group in which the secondary finder SF and the selector S arev located is busy, each of the chain relays;

such as 135,is energized and a circuit is completed for the common inalrefbusy relay 110.- Upon energizing, relay 1l() operates each of its armatures. At armature ll, re-

lay ll() removes battery from stepping magnet 1.45 of the secondary iinder allotter SFA so as to prevent the needless searching of this allotter Vat this time, there being` no finders available for pre-selection. `nit armature lll (a similar function is performed at each ofthe other armatures of the relay) relay 110 disconnects ground from conductor thereby removing groundat one point from the common conductor 43 over which the lower winding of relay 303,. Fig. 4, yis normally short circuited. It may be pointed out that the connection between conductors 64 and th'eyconductor 43 includes the jumper 54, conductor 48', spring 29 of the push button Q8 and. its resting contact, armature 35 and its resting contact, resting contact and armature 3l, and oft7 normal spring 25 and its lower contact. This operation does not have any particularlefiect at this time in case there are other primary lindersavailable in the saine group, but, is the saine operation as is performed when the primary iinderfPll itself isactually busy. As a further result of the energization of the maltebusy relay llt), Fig. 2, armature lll applies ground to conductor 53, which ground is eX- tended through the jumper 63 and conductor 48 tothe test conductor 47 of the primary 'finder Pl?, which is connected to the first contact in the bank of test wiper 847 of the primary Aiind'erallotter PFA-1, Fig. 4. The pniinary finder PF is thus rendered busy, even though it is not actually in use, to the rsaid allotter PFA-1. Accordingly, if the allotter is at this time standing upon the contacts ofthe primary finder PF, as shown in the drawings, it is automatically advanced in the hereinbefore described manner and anotherii'nder is preselected.

Assuming now that all the primary finders accessible to the two allotters, shown in Fig. 4, become busy, or that part of the finders are busy and the rennaining` idle ones are associated with busy secondary groups, ground is removed at all points from the common conductor 43, whereupon relay 371', Fig. 4, 'being'` no longer short circuited, energizes in series with the associated resistance 330 and disconnects stepping relay 346 from the test wipers 347 and 357 at armature 372, so as to stop the automatic testing operation of the two alotters at this time. tlf course the test wiper of thelallotter which happens to be on its bank at this time engages a grounded contact because all contacts inthe bank of each allotter are grounded at this time. Accordingly, a circuit is closed through theresting contactand armature 318 for relay 303. Re

lay 303 energizes to prevent a call from startthe test relay y346 again at armature 372. -lWhen this occurs, the Itwo allotters operatein the usual manner to pre-'select an idle primary linder and relay B deenergizes when an idle finder is pre-selected.,

Vhatis claimed is: f y

1. In a telephone system,V a plurality ot lines tens rela fs and units relays for register- 3 l v l C ing the numbers oi such lines, ak connection between one conductor-oi' each line vand the corresponding tens relay, a transfer relay, and means for energizing ,said transfer relay to disconnect each of said conductors from the corresponding tens relay and to connect suoli vconductor to the unit-s relay corresponding to the units designation of the corresponding line. y

2. In a telephone system, a plurality of lines, a line linder, tensrelays and units rec la s means responsive toa .calling condition v ing line, means including the tens relays of alower order thanthe energized one for count'- ing ott' and terminating the iirst series of iinpulses, and means including the units relays of a lower `order than the energized one tor counting oil and terminating the second series of impulses.

3. In a telephone system, subscribers lines dividedvinto groups,- a grouper" backwardV hunting finder switches lor each group of lines andhaving access thereto, secondary finder switches divided into groups and yhaving access to said iii'st finder switchesthrougli a system of trunk lines arranged so that the finders in each group of secondary tinder switches has access to one'finder in each primary group. I vc 4.111 atelephone trunking system, a plurality ot groups ot primary finder switches, plurality of groups ot secondary liiider switches, the secondary iind-ers in each group having access to a certain number of "iiiiders n in'each primary group, anda distributing esl .traine inserted between the said primary groups and the said secondary groups" by means of which any primary finder lmaybe readily rendered acce'ssibleto any group of secondary finders. 5. In a telephone trunlring system, means vfor connecting calling lines with trunlr lines,- said means comprising directiyely controlled primary finders for lor-ating the calling lines, f and automatic tree limiting secondary linders for locating engaged primary finders and for ,connecting themwith the said trunk lines.

6. In a telephone truiilring system, serially related primary ausA` Secondary iinders tor* connecting calling lines with trunk lines, coinmon impulse transmittino` mechanism vfor f directively o'peratinga primary linder to` connect with any calling line without testingany .other lines, and means .tor causing a secondary finder to test said primary finders in rotation and connect with the one which isiconnectedwith the calling line.

7. In a telephone trunlring system, a group ot secondary finder switches, an allotter common to said switches, a plurality of groups ol' primary finder switches each containing a i iinderaccessible to said secondary finders, an allotter common to eachv primary group, and means in each primary allotter lor controllingsaid secondary allotter.

8; ln telephone ti'unlring system, a group of primary linderswitclies, an allotter 'for pre-selecting idle primary iinders, a group or group of se'coii'daryiiiiders haring access to a limited number of i'inders in each of said primary groups, and means etlectiye in case all said secondary finders ,become busy for prevent-ing the starting yof aiiycprimary linder to which such secondary linders have access.

l1. In a telephone trunlring y system primary andsecondaryiinder switches 'for connecting calling lines with trunk lines, a switching relay in each finder switch tor closing rthe talking circuit, means responsive yto a call for starting a primary finder' and a secondary linder, means for enei`-gizingl the switching lrelay in the operated secondary iinder when such :tinder finds the primary iinder which has been started, and means common toa group oiC `Ji'iinary `Finders i'or'holding the energized switching relay energized until the started primary inder locates the calling line;

12.111 telephone ltrunking system primary' and `secondary finder switches i''or connecting calling lines` with trunlr lines, a switching rela-y in veac/h Vfinder switch `for closing the talking circuit, meansresponsive to a call for starting a primary finder and a secondary linder, 'means effective only when both v linder switches hayestopped 'for energizing the Vswitching` relay in the primary linl means for energizingt'he switching rela,

the secondary linder at once wiicnsuch li. stops regardlessof whether the primary finder has stopped or not, andine'ans common to the primary linder and other finders in the same group for maintaining the switching relay ofthe secondary finder energized in case such secondary finder stops before the primary finde-r. y

13. ln a finder system, subscribers7 lines, tens relays normally connected to said lines, units relays, means responsive to a call for energizing the proper tensy relay, and means responsive to the operation oli the energized tens relays for disconnecting said lines from said tens relays and for connecting them with said units rela-ys. p p

ll. ln a finder system, tens and units relays connected to the same pole ofl the exchange battery, subscribers lines, normally closed contacts through which said lines are conF nected to said tens relays, and. normally open contacts operable to connect said lines to said units relays.

i nected to said tens relays, normally open contacts operable to connect saidlines to saidA units relays, and means responsive to the operation oitanyk tens relay for opening the normally closed contacts and for closing the normally open contacts.

16. ln a finder system, tens and units relays connected to the same pole of the exchange battery, subscribers lines, normally closed contacts through which said lines are connected to said tens relays, normally open contacts operable to connect said lines to said units relays, means responsive to the operation of any tens relay for opening the normally closed contacts and for closing` the. normally open contacts, other contacts for disconnecting the lines from said units relays, and means responsive to the operation of any units relay for operating said other contacts.

17. ln a finder system, subscribers lines, each having one conductor normally connected to the same pole ofV the exchange battery,

`tens relays normally connected between the other conductors of vsaid lines and the other pole of the exchange battery, means respon sive to the energization of any tens relays for disconnecting all said first mentioned con` ductors from a battery, and contacts on the energized tens relay for re-connecting to the battery the conductors of those lines which have the same tens designation as the ener-` gized tens relay.

18. In a linder system, subscribers lines, tens relays normally connected to said lines,

units relays, means responsive to the opera-- tion of any tens relay for shifting the lines from the tens relays to the said units relays, and means for preventing said units relays from responding to calls over lines other than those lines which have the same tens designation as the operated tens relay.

19;. In av finder system, subscribers4 lines, iinder switches, tens and unitsy relays, and means: for operating said relays as counting relays to control said finders.

y2.0. ln a iin-der System, subscribers lines, Ender: switchessendingj apparatus tor operating said finders, cou-ltiirgrelays for con trollingsaid sending; apparatus, and means for energizing one of said counting relaysover a. calling; subscribersline to pre-determine the extent of a sending operation.

21. In ai finder system, a group of sul scribiers? lines, a finder,Y relays each common to a subgroupv off said lines, means 'for ener gizing one of said relays responsive to a call, sendingapparatus for transmittingl impulses to said finder and also to said relays, thesaid relays responding successively, and means for stopping the transmission of mr V pulses responsive to the en'ergization of theparticular relay immediately preceding the one which energized responsive to` the cal-l.

22. In a finder systcnfr,` subscrilY lines,- finder switches, sending appai-'attrsr for oper ating` said finders, counting relays, energizing circuits for said relays including said lines, and other local energizing circuits` for said relaysv controlled by said sendingL apparatus.

23. InY aik telephonefsystei'n, any automatic switch, a series of counting relays, a circuit for transmitting impulses to said switch and to said relays, means for closing said circuit at one point by energizing one of said relays, and means for opening said circuit responsive to theenergization of the next pre- A ceding relay by an impulse transmitted over said circuit.

24. In a switch control system, an impulse transmit-ting circuit, a Y series of counting relays, contacts on each relay except the first for closing said circuit, and contacts on each relay except the last for opening said circuit. v

25. ln a switch control system, a series oit counting relays, a pair of normally open contacts on each relay except the first, a pair of normally closed contacts on each relay except thelast, circuit arrangements whereby each pair of normally closed contacts'isconnected inr series with the pair of normally open contacts on the next succeeding relay, and an impulse transmitting circuit connect 4ed in multiple to one Contact of each pair of normally open contacts.

26. In a switch control system, an impulse transmitting circuit, a series of counting re lays, a plurality of branches of said circuit, the number of branches being one less than the number of relays, contacts on each relay except the firsty for closing Vone of said branches, and contacts on each relay except the last for opening the branch which adapted to lbe closed by the next succeeding relay.

operating said switch under the control oi said relays to establish a connection with said line. -f l 28. In a linder system, a group of sub- ,scribers5 lines divided into aplurality of sub groups, two motion finder switches having access to said lines, a register relay for each of said sub groups, means responsive to the initiation of a call on one ot' said lines for energizing theregister relay corresponding to the sub group containing the calling line, a second group of register relays corresponding in number to the nuinberot' lines in each of said sub groups, means responsive to the energization of said sub group register relays r'or connect-ingsaid second group oi register relays to the line in the sub group containing the calling line, means controlled over the calling line for energizing the register relay corresponding thereto, and means controlled by said energized register relay and the deenergized register relays of lower order for directing one of said iinders to vestablish a connection With said calling line.

29. ln a finder system, a group or suberibers lines divided into a plurality ot sub groups, two motion nder switches having access to said lines, a register relay for each oit said'sulo groups, means responsive to the initiation of a call on one of said lines for energizing the register relay corresponding to the sub group containing the calling line` a second group of register relays corresponding in number to the number of lines in each of said sub groups, means responsive to the energization ot said sub group register relay for connecting said second group ot register relays to the line in the sub group containing the calling lines, means controlled over the calling line for energizing the register relay corresponding thereto, means responsive to the energization of said line register relays for disconnecting the remainder of said line register relays from said lines, and means controlled by said energized relay and the deenergized register relays of the lower order .ior directing one of .said iinders to establish a connection With said calling line. K

Vlin Witness whereof, Iy hereunto subscribe my name this 19th day of August, A. D., 1924.

RUDOLPH F. STEHLK.; 

